Numerical simulation of hydrogen dispersion in an open-ended rectangular channel

In this work, large-eddy simulations of hydrogen dispersion from turbulent subsonic hydrogen-gas emissions in a 5.8 × 0.9 × 0.8 m open-ended channel are described. Such numerical modeling of hydrogen-related processes can provide new insights into the safety aspects of hydrogen, an increasingly more common energy carrier, particularly related to explosion hazards. Ten simulations, with jet mass flow rates ranging from 0.08 g/s to 1.27 g/s, have been simulated using the open-source OpenFOAM® 10 suite. The predicted concentrations in the channel are compared to corresponding experimental data, generally showing good agreement. Two distinct dispersion regimes are observed from the numerical data; a strongly stratified “filling box” regime is found for hydrogen mass flows g/s, whereas a more homogenized “fading box” regime emerges for higher mass flows. Based on the local Froude number in the channel, a novel model for the momentum length scale of the hydrogen jet is proposed, applicable to downward, strongly buoyant (i.e., non-Boussinesq) jets. It is demonstrated that the ratio of this length scale to the vertical length scale of the geometry can be used to predict the dispersion regime, which may benefit simplified predictive models for hydrogen concentrations and, consequently, ignition risks.